1. Field of the Invention
This application relates to a dry cryogenic shipping container and, more specifically, to a dry cryogenic shipping container having a removable absorbent.
2. Background Information
Cryogenic shipping containers are used to transport materials at temperatures well below the freezing point of water. The materials transported at cryogenic temperatures are typically biologically active, such as, but not limited to, tissue samples and microorganism cultures. Hereinafter these materials will be identified as “use materials.” The typical cryogenic shipping container, similar to many storage devices for cryogenic liquids, included a Dewar flask, or similar construct, having an outer shell, an inner shell, and a vacuum therebetween. The inner and outer shells were coupled at a neck which defines a passage into the interior of the inner shell. A shipper core, typically a hollow cylinder, was disposed within, and coupled to, the inner shell. The inner shell had an inner diameter that was greater than the diameter of the shipper core. Thus, there was an annular gap between the shell and the shipper core. The shipper core may have also included a support structure for holding another containment device, such as, but not limited to, a canister or sample container.
When prepared for transport or storage, a cryogenic shipping container included a use material disposed in a sample container, which in turn was contained in a removable canister. The canister was then disposed in the shipper core. The shipper core, as noted above, was coupled to the inner shell. A cryogenic liquid was disposed in the annular gap between the shell and the shipper core. The container was closed by an insulated cap as was known in the art. This basic configuration, while useful, allowed cryogenic liquid to slosh about within the inner shell. Such a fluid movement is undesirable as it enhanced evaporation; the cryogenic liquid could splash on the use material, and cryogenic liquids can be dangerous to touch.
To reduce the amount of free cryogenic liquid in a cryogenic shipping container, absorbent materials were disposed in the annular gap. The absorbent materials were typically a rigid foam or another moldable material that could be disposed within the inner shell while maintaining a cavity sized to accept the shipper core. This absorbent material was, effectively, sealed in the inner space of the inner shell when the shipping core was coupled to the inner shell. In operation, the cryogenic liquid was poured into the inner space and allowed to be absorbed by the absorbent material. Any excess cryogenic liquid was removed prior to placing a sample container in the shipping core. As the cryogenic liquid was trapped in the absorbent materials, this type of cryogenic shipping container was identified as a “dry” cryogenic shipping container.
The disadvantage to using the dry cryogenic shipping container is that the absorbent material may become contaminated by the use materials. Once the absorbent materials become contaminated, the cryogenic shipping container should not be used again. Thus, the relatively expensive cryogenic shipping container may be rendered useless due to the contamination of the relatively inexpensive absorbent material.
There is, therefore, a need for a dry cryogenic shipping container that may be reused.
There is a further need for a dry cryogenic shipping container having a removable absorbent material.